The lipogenic enzyme ATP-citrate lyase (ATP-CL) is subject to dietary regulation by sucrose. The level of hepatic ATP-CL is increased several fold in the sucrose refed rat over the level found in the liver of starved rats. This induction of ATP-CL by dietary sucrose has been shown to be due to an increased amount of ATP-CL. This increased amount of ATP-CL has been shown to be due to an increase in the rate of synthesis of ATP-CL rather than to a decrease in the rate of degradation of ATP-CL. Dietary sucrose either stimulates the release (or synthesis) of a substance or is converted to a substance which is the molecular inducer of ATP-CL. The identity of this molecular inducer, the step of protein synthesis affected by the molecular inducer, and the mechanism of induction of ATP-CL are not known. The following research proposal is designed to determine the step of protein synthesis which is acted on by the molecular inducer to yield increased synthesis of ATP-CL. A homogenous preparation of rat liver ATP-CL will first be prepared in order to make an antibody specific against rat liver ATP-CL. This anti ATP-CL will be used to identify nascent and completed ATP-CL and to precipitate polysomes containing nascent ATP-CL. The determination of the puromycin released nascent ATP-CL, in vitro completed ATP-CL and polysomes containing nascent ATP-CL during starvation and sucrose refeeding will determine at which step, if any, of translation (i.e. chain initiation, chain elongation and chain termination) sucrose exerts its molecular effect. The amount of ATP-CL mRNA will be measured by determining the amount of mRNA in the polysomes containing nascent ATP-CL specifically percipitated by anti ATP-CL and by measuring the effectiveness of mRNA isolated from the different dietary states to produce ATP-CL (measured by precipitation with anti ATP-CL). If sucrose is shown to increase the amount of ATP-CL mRNA, then the rates of synthesis and degradation of ATP-CL will be determined by following the appearance and disappearance of (C14) uridine in the mRNA fraction of polysomes containing nascent ATP-CL precipitated with anti ATP-CL.